When digital audio communication devices are used in a noisy environment (typically inside a car), the latter can greatly disturb an audio signal and consequently degrade the quality of the communication.
According to known techniques, noise suppressors or cancellers are inserted to resolve this problem, acting on the signal picked up by a microphone, prior to specific processing of the audio signal.
According to a first known technique, an echo or noise cancellation and reduction device is installed between a microphone designed to pick up an audio signal and an audio signal processing device. This device improves the useful signal to noise ratio or suppresses the echo so that the signal can then be processed under optimal conditions. However, this prior art technique requires a specifically dedicated device, which has the inconvenience of generating additional costs and increased application complexity.
According to a second known technique, the noise reduction function, based on the use of a Fast Fourier Transform (FFT) applied to a continuous flow of speech samples, is integrated into the digital communication device. In the first instance, the flow of samples is cut into windows of 256 samples obtained via the application of a formatting window, the windows half overlapping (the first 128 samples of a window corresponding to the last 128 samples of the preceding window). An FFT is applied to each window and then the result of the FFT is processed by a noise or echo cancellation or reduction function.
Then, the result of this function is processed via an Inverse Fast Fourier Transform (IFFT) so as to reconstitute a flow of speech samples which could be processed via a speech processing function.
An inconvenience of this prior art technique is that it is relatively complicated to implement.
The invention according to its different aspects is notably purposed to compensate for these inconveniences of the prior art.
More precisely, one purpose of the invention is to provide a method and an audio processing device in a device which allows a reduction in the complexity of processing based on a mathematical transformation being applied to data blocks whilst optimising the audio processing being applied to audio frames.
Another purpose of the invention is to optimise the integration of the processing based on a mathematical transformation and of the audio processing.
A purpose of the invention is also to optimise the duration of this processing.
Another purpose of the invention is to reduce the computing power needed for this processing.